Document Detail

Requirement for flow in the blockade of endothelium-derived hyperpolarizing factor (EDHF) by ascorbate in the bovine ciliary artery.
MedLine Citation:
PMID:  15237098     Owner:  NLM     Status:  MEDLINE    
We previously reported that ascorbate inhibits endothelium-derived hyperpolarizing factor (EDHF)-mediated vasodilatation in the bovine perfused ciliary circulation and rat perfused mesentery, but not in rings of bovine or porcine coronary artery. In this study, we have compared the ability of ascorbate to inhibit EDHF-mediated vasodilatation in a single vessel, the bovine long posterior ciliary artery, when perfused and when mounted as rings in a myograph. Both in segments perfused at a flow rate of 2.5 ml min(-1) and in rings mounted in a myograph, bradykinin and acetylcholine each induced vasodilator responses that were mediated jointly by EDHF and nitric oxide, as revealed by their respective blocking agents, apamin/charybdotoxin, and L-NAME. Ascorbate (50 and 150 microm) induced a time (max at 2-3 h)-dependent inhibition of the EDHF-mediated component of vasodilatation to bradykinin or acetylcholine in perfused segments, but not in rings. Ascorbate (50 microm) failed to inhibit bradykinin-induced vasodilatation at a flow rate of 1.25 ml min(-1) or below, but produced graded blockade at the higher flow rates of 2.5 and 5 ml min(-1). Furthermore, using a pressure myograph where pressure and flow were independently controlled, it was confirmed that the inhibitory action of ascorbate (150 microm) was directly related to flow per se and not any associated changes in pressure. Thus, we have shown in the bovine ciliary artery that ascorbate inhibits EDHF-mediated vasodilatation under conditions of flow but not in a static myograph. The mechanism by which flow renders EDHF susceptible to inhibition by ascorbate remains to be determined.
Silvia Nelli; Fiona J Dowell; William S Wilson; Alison Stirrat; William Martin
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Publication Detail:
Type:  Comparative Study; In Vitro; Journal Article; Research Support, Non-U.S. Gov't     Date:  2004-07-05
Journal Detail:
Title:  British journal of pharmacology     Volume:  142     ISSN:  0007-1188     ISO Abbreviation:  Br. J. Pharmacol.     Publication Date:  2004 Aug 
Date Detail:
Created Date:  2004-07-30     Completed Date:  2005-08-04     Revised Date:  2013-06-09    
Medline Journal Info:
Nlm Unique ID:  7502536     Medline TA:  Br J Pharmacol     Country:  England    
Other Details:
Languages:  eng     Pagination:  1081-90     Citation Subset:  IM    
Copyright Information:
Copyright 2004 Nature Publishing Group
Division of Neuroscience & Biomedical Systems, Institute of Biomedical & Life Sciences, West Medical Building, University of Glasgow, Glasgow, G12 8QQ, Scotland.
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MeSH Terms
Ascorbic Acid / pharmacology*
Biological Factors / antagonists & inhibitors*,  physiology
Ciliary Arteries / drug effects*,  physiology
Dose-Response Relationship, Drug
Muscle, Smooth, Vascular / drug effects,  physiology
Regional Blood Flow
Vasodilation / drug effects*,  physiology
Reg. No./Substance:
0/Biological Factors; 0/endothelium-dependent hyperpolarization factor; 50-81-7/Ascorbic Acid

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